Thu, 25 Nov 2004

For years I've been using CD-R for backups, especially of photos.
Every now and then I see an article about CD longevity (people are
all over the map about how long these things are supposed to last;
here's
one useful article)
and wonder if I should worry.

It turns out the answer is yes. Yesterday I was looking for some
photos from mid-2001, and discovered that about 80% of the files on
the CD wouldn't read in my DVD reader -- "I/O error". Fortunately,
my DVD writer could read about 80% of the files (maybe it's a little
slower, or something? Or just newer?)

A subsequent flurry of copying my older CD-Rs found read errors on
many discs two and three years old.
The two worst both had sticky labels on them.
In one case (some images I didn't want to lose), I burned two
copies of the same disc, printed a pretty label on one and marked
the other with a Sharpie. The Sharpie disc read fine; the
labelled disc had massive errors and was all but unreadable.
The advice saying not to print labels for CDs meant for
backup appears to be accurate; but even without labels,
they're not reliable.

I'm not sure of a better backup solution, though. I don't trust
longevity for anything magnetic (I've seen too many tapes and floppies fail).
One solution I'm trying is an IDE disk sitting in an external
USB2/firewire enclosure: it can stay powered off most of the
time, and copies are fast. But a disk has a lot of failure modes
(magnetics, head crash, motor). Safer would be two external drives,
kept in sync.